Microstructural Study of CrNiCoFeMn High Entropy Alloy Obtained by Selective Laser Melting

Abstract

The high entropy alloy (HEA) of equiatomic composition CrNiFeCoMn and with FCC crystal structure was additively manufactured in a selective laser melting (SLM) process starting from mechanically alloyed powders. The as-produced alloy shows fine nitride and σ phase precipitates, which are Cr-rich and stable up to about 900 K. The precipitates increase in number and dimensions after long-period annealing at 900–1300 K, with a change in the HEA mechanical properties. Higher aging temperatures in the furnace, above 1300 K, turn the alloy into a single FCC structure, with the disappearance of the nitride and σ phase precipitates inside the grains and at the grain boundaries, but still with the presence of a finer Cr-rich nitride precipitation phase. These results suggest that the as-produced HEA is a supersaturated solid solution at low and intermediate temperature with nitrides and σ nanostructures.